Reporting: add section about progress reporting

Author: jrfnl

wiki/Reporting.md

@@ -1,4 +1,5 @@
 ## Table of contents
+* [Progress reporting](#progress-reporting)
 * [Printing Full and Summary Reports](#printing-full-and-summary-reports)
 * Other Report Types
     * [Checkstyle](#printing-a-checkstyle-report)
@@ -23,6 +24,27 @@
 
 ***
 
+## Progress reporting
+
+To see progress reporting while scanning a code base, use the `-p` command line argument.
+
+Legend for the progress indicators:
+
+| When scanning with | Indicator    | Means:                                                    |
+| ------------------ | ------------ | --------------------------------------------------------- |
+| `phpcs`/`phpcbf`   | `S`          | Skipped file                                              |
+| `phpcs`            | `E` (red)    | Non-fixable errors found in the file                      |
+|                    | `E` (green)  | Fixable errors found in the file                          |
+|                    | `W` (yellow) | Non-fixable warnings found in the file                    |
+|                    | `W` (green)  | Fixable warnings found in the file                        |
+|                    | `.`          | No errors or warnings found in the file                   |
+| `phpcbf`           | `F` (green)  | Fixed errors or warnings in the file                      |
+|                    | `E` (red)    | Unfixable errors or warnings in the file (fixer conflict) |
+|                    | `.`          | No errors or warnings found in the file                   |
+
+<p align="right"><a href="#table-of-contents">back to top</a></p>
+
+
 ## Printing Full and Summary Reports
 When running a scan, by default, the full report is displayed.